1. Field of the Invention
The present invention relates to an improvement in an electromagnetic switch matrix for automatic exchanges, hybrid computers and the like, in which magnetically responsive switch elements are penetrated through a magnetic shunt plate and provided with excitation coils at cross-points where row signal lines and column signal lines intersect at right angles to each other.
2. Description of the Prior Art
In a switch matrix employing sealed switches, a reversed-magnetization no-current holding type switch element called "Ferreed switch" has been used.
In such Ferreed switches, a desired number of sealed switches are inserted between two "remainders", planar magnetic cores made of semi-hard magnetic material. At the center of these planar magnetic cores is disposed a magnetic shunt plate forming a magnetic shunt path. Above and below the magnetic shunt plate are respectively disposed two sets of windings, each set consisting of windings of N and 2N in the number of turns, respectively, so as to effect the differential excitation.
The operation of the Ferreed switch is such that when a driving current is fed to both the two sets of the windings, the magnetization of the planar magnetic core is in the same direction at a point above and below the magnetic shunt plate thereby to close the sealed switch. When the driving current is fed to only one set of the windings, the magnetization is in opposite directions at a point above and below the magnetic shunt plate, so that the sealed switch is opened due to elasticity of the contact springs.
In the Ferreed switch matrix, a desired number of Ferreed switches are disposed in matrix form, one of the two sets of the windings are connected in common in the row direction, while the other set of windings are connected in common in the column direction to constitute the switch matrix.
However, in such a switch matrix, since driving currents are fed simultaneously to the windings connected in common along a row and to the windings connected in common along a column, the sealed switches located at the cross-points in rows and columns associated with a particular cross-point are all magnetized in the opposite directions at a point above and below the magnetic shunt plate, and are thereby opened. Accordingly the sealed switches at a plurality of cross-points in the same row or in the same column cannot be simultaneously closed.
An electromagnetic switch matrix designed to overcome this difficulty is proposed in the U.S. Pat. No. 3,953,813 issued to Yano et al. and U.S. Pat. No. 3,982,216 issued to Mitsuhashi et al.
These conventional electromagnetic switch matrices of divisional excitation type comprise a desired number of sealed switches having self-holding capabilities and arrayed in a matrix form, a magnetic shunt plate for forming magnetic shunt paths disposed at the center portions of the contacts in these sealed switches, first and second winding means for controlling said sealed switches aligned along a column between said magnetic shunt plate and said first winding means and on said the other side of said magnetic shunt plate outside of said second winding means, respectively, and means for short-circuiting said second and third winding means in a selected row and a selected column, respectively, when required, said first to fourth winding means having substantially the same number of turns, a magnetic circuit on one side of said magnetic shunt plate and a magnetic circuit on the other side of said magnetic shunt plate being constructed in a magnetically symmetrical form, and said first to fourth winding means are connected in such polarities that magnetic fields generated by said first and fourth winding means are directed in one direction while magnetic fields generated by second and third winding means are directed in the other direction.
In such a switch matrix, when a sealed switch at a particular cross-point is to be closed, a first driving current is fed to all the first to fourth winding means pertinent to that particular cross-point to open the sealed switches at the associated cross-points (the other cross-points in the same row and in the same column as the particular cross-point) by magnetizing the sealed switches in the opposite directions to each other on the respective sides of the magnetic shunt plate with the first and third winding means or the second and fourth winding means, then the second and third winding means are short-circuuited with said means for short-circuiting the second and third winding means to feed a second driving current only to the first and fourth winding means, thereby to close the sealed switch at the particular cross-point.
In such a switch matrix, it is possible to effect the simultaneous closing of switches at a plurality of cross-points in the same row or in the same column, because the separate driving currents are fed for opening and closing, respectively, of the cross-point switch. However, in this type of switch matrix, the direction of remanent magnetization at the associated cross-points that is determined by the first driving current needs to coincide with the direction of the excitation magnetic field applied to the associated cross-points by the second driving current, and if these magnetic fields do not coincide with each other, the associated cross-point switches tend to operate erroneously.
Thus, the particular cross-point selectively closed first and another cross-point not associated with the particular cross-point (a cross-point other than the cross-points either in the same row or in the same column as the particular cross-point) is then selectively closed. Under this state, another cross-point in the same row as the particular cross-point is selectively closed for double connection, with the direction of remanent magnetization and the direction of the excitation magnetic field generated by the second driving current at the associated cross-points being different from each other. This makes it necessary to effect the double connection such that immediately after the particular cross-point has been selectively closed, another cross-point in the same row as the particular cross-point should be selectively closed.